The zeddy that came in the bundle with my Memotech keyboard is in lovely condition, produces a reasonable picture even on my full HD lcd screen and even has the till receipt stapled to the shop guarantee card. So rather than refurbish it I have just changed the keyboard membrane (which was beyond trimming) and will sell it on (I really have enough tribbles zeddies now) as a nice collectors piece.
It works fine but if I plug in both a ZXPand and ChromaSCART I just get a dark screen and nothing going on. If I plug in just one or the other it works fine. Both work fine combined on other zeddies.
If I plug in the Memotech RAM pack that came with it and the ChromaSCART I get the same.
Is it struggling for power with the old regulator? (The engines cannie take it cap’n!)

Due to the amount of power required for those expansions, the 9V and 0V/GND circuits / conductors (including connectors) between the PSU and the expansions must be good. Inspect, clean, test (with the power off, use a good multimeter on the 200 ohms range, circuit resistance must be low, 0.1 ohms or lower).

Before changing the 7805, check that (1) making sure that the nut and bolt holding the heatsink and the 7805 are tight. If you have any heatsink compound/paste, remove the heatsink, clean off any existing compound (if any was used), smear a new thin film where the 7805 is pushed up against the heatsink, then reassemble.
And (2) the solder joints are good (if necessary, resolder them by removing the old solder, cleaning the pads and pins, then resoldering).

I wanted to keep it as original as possible due to its condition so don’t really want to change the 7805 if possible. I was mostly curious as I have never had one before that didn’t work with the two expansions connected.

I will check out the connections etc. and ensure the nut and bolt are tight.

I had put this on eBay last night with the comment that I could replace the regulator and caps if the new owner wanted me to.
It sold this afternoon and the new owner wanted me to.
So I have replaced the regulator (the nut was extremely tight) and the caps and now it runs both fine. I guess it was the regulator then!